System for an air maintenance tire assembly

ABSTRACT

A system is used with a pneumatic tire mounted on a wheel rim to keep the pneumatic tire from becoming underinflated. The first system includes a plurality of pumps attached circumferentially to the wheel rim, each pump having pump parameters, and a control valve for controlling inlet air into a tire cavity of the pneumatic tire. The control valve has valve parameters. The system predicts system performance under various configurations and conditions through use of the pump parameters and the valve parameters.

FIELD OF THE INVENTION

The present invention relates to a system and method for maintainingappropriate air pressure within a pneumatic tire. More specifically, thepresent invention relates to a rim mounted system for directing air intoa tire cavity of a pneumatic tire.

BACKGROUND OF THE INVENTION

Conventional pneumatic tires are designed to perform for relatively longperiods of time. In many cases, automobile tires are now expected tohave a useful service life of 30,000, 50,000, or 70,000 miles. However,even long-life pneumatic tires are subject to air pressure losses due topuncture by nails and other sharp objects, temperature changes, and/ordiffusion of air through the tire itself.

Since air diffusion reduces tire pressure over time, the pneumatic tiresare often continually underinflated. Accordingly, drivers mustrepeatedly act to maintain tire pressures or fuel economy, tire life,and/or vehicle braking and handling performance will be reduced. TirePressure Monitoring Systems (TPMS) have been proposed to warn driverswhen tire pressure is significantly low. Such systems, however, remaindependent upon a driver taking remedial action, when warned, tore-inflate a tire to the recommended pressure. It is desirable,therefore, to incorporate an air maintenance feature within a pneumatictire that will maintain recommended air pressure without requiringbothersome driver intervention.

SUMMARY OF THE INVENTION

A first system in accordance with the present invention is used with apneumatic tire mounted on a wheel rim to keep the pneumatic tire frombecoming underinflated. The first system includes a plurality of pumpsattached circumferentially to the wheel rim, each pump having pumpparameters, and a control valve for controlling inlet air into a tirecavity of the pneumatic tire. The control valve has valve parameters.The system predicts system performance under various configurations andconditions through use of the pump parameters and the valve parameters.

According to another aspect of the first system, the plurality of pumpsand the control valve define a multi-chamber pump configuration.

According to still another aspect of the first system, each pumpincludes one piston placed between two chambers.

According to yet another aspect of the first system, the two chambersare connected by a narrow passage having a one-way check valve.

According to still another aspect of the first system, the pumps are fitto the wheel rim, set P_(R)(i)=P_(L)(i)=P₀, i=1 to n (total number ofpumps used), set x(i)=0 and θ(i)=2π/n(i−1), P_(L)(0)=P₀ (always) andP_(R)(n+1)=P_(tire) (the tire cavity), calculate new x(i), P_(R)(i) andP_(L)(i), determine check valve status: if P_(R)(i)≧P_(L)(i)+Pcr, thencheck valve is open; if P_(L)(i−1)≧P_(R)(i)+Pcr, then adjacent checkvalve is open; balance pressure between connected chamber and resetcheck valve to close; and recalculate x(i), P_(R)(i) and P_(L)(i) untilno more open check valve.

According to yet another aspect of the first system, subsequent to theprevious aspect the wheel rim rotates to a predefined step angle,calculate new x(i), P_(R)(i) and P_(L)(i), determine check valve status:if P_(R)(i)≧P_(L)(i)+Pcr then check valve is open; ifP_(L)(i−1)≧P_(R)(i)+Pcr then adjacent check valve is open; balancepressure between connected chamber and reset check valve to close; andrecalculate x(i), P_(R)(i) and P_(L)(i) until no more open check valve.

According to still another aspect of the first system, the plurality ofpumps define a force control system with a maximum pumping capabilitydetermined by a piston of each pump moving a maximum distance withineach pump.

According to yet another aspect of the first system, each pump includesa first diaphragm limiting motion of a piston in a first direction and asecond diaphragm limiting motion of the piston in a second oppositedirection.

According to still another aspect of the first system, the system isdriven by two force a gravitation component and an accelerationcomponent.

According to yet another aspect of the first system, the pump parametersinclude a piston mass parameter, a first piston travel parameter, and asecond piston travel parameter.

A second system in accordance with the present invention models apneumatic tire mounted on a wheel rim and a pumping mechanism mounted onthe wheel rim to keep the pneumatic tire from becoming underinflated.The second system includes a plurality of pumps attachedcircumferentially to the wheel rim, each pump having pump parameters,and a control valve for controlling inlet air into a tire cavity of thepneumatic tire. The control valve has valve parameters. The secondsystem predicts system performance under various configurations andconditions through use of the pump parameters and the valve parameters.

According to another aspect of the second system, the plurality of pumpsand the control valve define a multi-chamber pump configuration.

According to still another aspect of the second system, each pumpincludes one piston placed between two chambers.

According to yet another aspect of the second system, the two chambersare connected by a narrow passage having a one-way check valve.

According to still another aspect of the second system, the pumps arefit to the wheel rim, set P_(R)(i)=P_(L)(i)=P₀, i=1 to n (total numberof pumps used), set x(i)=0 and θ(i)=2π/n(i−1), P_(L)(0)=P₀ (always) andP_(R)(n+1)=P_(tire) (the tire cavity), calculate new x(i), P_(R)(i) andP_(L)(i), determine check valve status: if P_(R)(i)≧P_(L)(i)+Pcr, thencheck valve is open; if P_(L)(i−1)≧P_(R)(i)+Pcr, then adjacent checkvalve is open; balance pressure between connected chamber and resetcheck valve to close; and recalculate x(i), P_(R)(i) and P_(L)(i) untilno more open check valve.

According to yet another aspect of the second system, subsequent to theprevious aspect, the wheel rim rotates to a predefined step angle,calculate new x(i), P_(R)(i) and P_(L)(i), determine check valve status:if P_(R)(i)≧P_(L)(i)+Pcr then check valve is open; ifP_(L)(i−1)≧P_(R)(i)+Pcr then adjacent check valve is open; balancepressure between connected chamber and reset check valve to close; andrecalculate x(i), P_(R)(i) and P_(L)(i) until no more open check valve.

According to still another aspect of the second system, the plurality ofpumps define a force control system with a maximum pumping capabilitydetermined by a piston of each pump moving a maximum distance withineach pump.

According to yet another aspect of the second system, each pump includesa first diaphragm limiting motion of a piston in a first direction and asecond diaphragm limiting motion of the piston in a second oppositedirection.

According to still another aspect of the second system, the system isdriven by two force a gravitation component and an accelerationcomponent.

According to yet another aspect of the second system, the pumpparameters include a piston mass parameter, a first piston travelparameter, and a second piston travel parameter.

A pumping mechanism for use with the present invention is used with apneumatic tire mounted on a wheel rim to keep the pneumatic tire frombecoming underinflated. The pumping mechanism includes a plurality ofpumps forming a linear belt and subsequently being attachedcircumferentially to the wheel rim, a plurality of pump holdersinterconnecting the plurality of pumps in a linear configuration, and acontrol valve for controlling inlet air into a tire cavity of thepneumatic tire.

According to another aspect of the pumping mechanism, the pumpingmechanism provides a low profile and effective multi-chamber pump systemmounted inside the wheel rim with no significant modification to thewheel rim and no modification to pneumatic tire.

According to still another aspect of the pumping mechanism, the pumpingmechanism utilizes gravitational force changes during rotation of thepneumatic tire.

According to yet another aspect of the pumping mechanism, each pumpincludes a piston body moving against a pair of diaphragms.

According to still another aspect of the pumping mechanism, the pistonbody of each pump travel in a first direction and an opposite seconddirection per each revolution of the pneumatic tire.

According to yet another aspect of the pumping mechanism, load on thepneumatic tire does not affect frequency of pumping action of thepumping mechanism.

According to still another aspect of the pumping mechanism, theplurality of pumps includes 4 to 10 pumps and 4 to 10 pump holdersconfigured circumferentially on a belt forming a loop and fittingcircumferentially within a middle groove of the wheel rim.

According to yet another aspect of the pumping mechanism, the controlvalve is shaped similarly to the pumps such that the control valve isplaced in a space between the beginning and the end of the belt.

According to still another aspect of the pumping mechanism, the pumpholders have adjustable lengths that multiple sizes of wheel rim.

According to yet another aspect of the pumping mechanism, the pumpingmechanism further includes a filter unit connected in series with thepumps and pump holders.

A pneumatic tire for use with the present invention is mounted to awheel rim to keep the pneumatic tire from becoming underinflated. Thepneumatic tire includes a plurality of pumps forming a linear belt andsubsequently being attached in series to the wheel rim, a plurality ofpump holders interconnecting the plurality of pumps in a linearconfiguration, and a control valve for controlling inlet air into a tirecavity of the pneumatic tire. The pumps function when mounted in a firstcircumferential direction on the wheel rim or a second oppositecircumferential direction on the wheel rim.

According to another aspect of the pneumatic tire, a plurality of checkvalves maintain air flow in the pumps in a single direction.

According to still another aspect of the pneumatic tire, a check valveis adjacent each side of the control valve.

According to yet another aspect of the pneumatic tire, the control valveis disposed at an air let to the pumps.

According to still another aspect of the pneumatic tire, the controlvalve is disposed at an air outlet of the pumps into a tire cavity ofthe pneumatic tire.

According to yet another aspect of the pneumatic tire, the control valveis disposed in a bypass of the pumps.

According to still another aspect of the pneumatic tire, load on thepneumatic tire does not affect frequency of pumping action of the pumps.

According to yet another aspect of the pneumatic tire, the plurality ofpumps includes 4 to 10 pumps and 4 to 10 pump holders configuredcircumferentially on a belt forming a loop and fitting circumferentiallywithin a middle groove of the wheel rim.

According to still another aspect of the pneumatic tire, the controlvalve is shaped similarly to the pumps such that the control valve isplaced in a space between the beginning and the end of the belt.

According to yet another aspect of the pneumatic tire, the pump holdershave adjustable lengths that multiple sizes of wheel rim.

DETAILED DESCRIPTION OF DRAWINGS

The following drawings are illustrative of examples of the presentinvention.

FIG. 1 is a schematic representation of part of a system in accordancewith the present invention.

FIG. 2 is a schematic representation of part of a system for use withthe present invention.

FIG. 3 is a schematic representation of another part of the system ofFIG. 2.

FIG. 4 is a schematic representation of another example system for usewith the present invention.

FIG. 5 is a schematic representation of part of the example system ofFIG. 4.

FIG. 6 is a schematic representation of part of still another examplesystem for use with the present invention.

FIG. 7 is a schematic representation of another part of the examplesystem of FIG. 6.

FIG. 8 is a schematic representation of still another part of theexample system of FIG. 6.

FIGS. 9A & 9B illustrate the piston mass effect on pumping capabilityand pumping pressure.

FIGS. 10A & 10B illustrate the number of pistons effect on pumpingcapability and pumping pressure.

DETAILED DESCRIPTION OF EXAMPLES OF THE PRESENT INVENTION

As shown in FIGS. 2 through 8, an air maintenance tire system 10 for usewith the present invention may provide a low profile and effectivemulti-chamber pump system that may easily mount inside of a wheel rim 12with no significant modification to the wheel rim (minor modificationmay be required for air inlet having two stems). Further, the airmaintenance tire 10 requires no significant changes to tire/wheelassembly or tire/wheel performance.

The air maintenance tire 10 may include a pumping mechanism, pumpdriving mechanism, or pump 14, utilizing gravitational force changesduring rotation of the air maintenance tire. The pump driving mechanism14 may include use of a mass of a piston body 16 moving against a pairof diaphragms 19 or an external mass (not shown) driving the piston bodyusing a cam/gear system. If the mass of the piston body 16 is used, thepump driving mode may be based on force control. If a cam/gear systemand external mass are used, gravitational force may drive gear rotationand convert this rotation to controllable displacement, as described inU.S. application Ser. No. 14/091,885, Air Maintenance Tire Assembly,herein incorporated by reference.

As the tire/wheel rotates, the piston body 16 may travel in a forwarddirection and an opposite backward direction per each revolution therebyproducing a high pumping frequency. Thus, higher vehicle speed mayprovide higher pumping frequency. The parameters of the pumping actiondepend upon the mass and angular velocity of the tire/wheel assembly.Tire load or other external conditions may not effect pumping action.

Due to an amplification effect, the compression of the pump drivingmechanism 14 may be defined as:

R=(r)^(2n)

where

R: system compression ratio

r: ingle chamber compression

n: number of pump in the sys e

Thus, a high compression ratio for each pump 18 is not necessary toachieve a high compression ratio (e.g., low force and/or deformation mayproduce high compression).

The pump driving mechanism 14 may include 4 to 10 pumps 18 and pumpholders 20 may be configured linearly on a belt forming a loop andfitting circumferentially in a middle groove of the wheel rim 12(radially innermost part of the wheel rim). A control valve 22 may beshaped similarly to the pumps 18 and may be placed in a space betweenthe beginning and the end of the belt. Pump holders 20 may haveadjustable lengths that fit any size of wheel rim 12.

A passage connection from a first valve stem to the control valve inletport may be connected after the belt is secured to wheel rim 12 (FIG.4). The control valve 22 may include a filter unit 30. The pump drivingmechanism 14 may be bi-directional and mounted in either direction. Thecontrol valve 22 may include an adjustment for varying a set pressurefor the tire cavity. The pump driving mechanism 14 thus may have a lowprofile around the wheel rim 12 that in no way interferes with tiremount/dismount and provides clearance in the tire cavity for impactsincurred (cleat or pothole) during driving of the vehicle. Further, the360° design (FIG. 4) of the pump driving mechanism 14 may be a balancedconstruction in no way degrading the balance of the tire/wheel assembly.

FIG. 6 shows of an example configuration having four pumps 18, six checkvalves 28, a control valve 22, and a filter 30. This configuration mayscale to n pumps 18 with the control valve 22 controlling air inlet intothe configuration from outside of the tire 10. The check valve 28 to theleft of the control valve 22 in FIG. 6 may be optional.

FIG. 7 shows of another example configuration having four pumps 18, fivecheck valves 28, a control valve 22, and a filter 30. This configurationmay scale to n pumps 18 with the control valve 22 controlling air outletfrom the configuration to the tire cavity. The control valve 22 may beplaced in a bypass of the pumps 18.

FIG. 8 shows of still another example configuration having four pumps18, five six check valves 28, a control valve 22, and a filter 30. Thisconfiguration may scale to n pumps 18 with the control valve 22controlling air outlet from the configuration to the tire cavity. Thecontrol valve 22 may be placed in series with the n pumps 18.

A pumping system, theory, or analytical model 100 in accordance with thepresent invention may define behavior of the multi-chamber pump systemdescribed above (FIGS. 2-8). Such a system may be converted to suitablecomputer codes as an analytical pumping model. This model may design andpredict system performance under various configurations and conditionsfor both consumer and commercial air maintenance tire systems.

There may be n pumps spaced equally about the circumference of the wheelrim 12. Each pump 18 may include one piston 16 placed between twochambers 101, 102, as described above (FIG. 2). The two chambers 101,102 may be connected by a narrow passage having the one-way valve 28, orCV(i), with i=1 to n (FIGS. 4-8). CV(n+1) and CV(n+2) may be placed atthe air inlet and outlet of the system 10, and between the pumps 18,CV(i), i=1 to n.

 For example (FIG. 1): Step 0  Flow flat assembly to fit to rim (FIGS. 4& 5);  Set P_(R)(i)=P_(L)(i)=P₀, i=1 to n (total number of pumps 18used);  Set x(i)=0 and θ(i)=2π/n(i−1);  P_(L)(0)= P₀ (always) andP_(R)(n+1)=P_(tire) (the tire cavity);  Calculate new x(i), P_(R)(i) andP_(L)(i);  Determine check valve status:   If P_(R)(i) ≧ P_(L)(i)+Pcr,then icv(i) is open;   If P_(L)(i−1) ≧ P_(R)(i)+Pcr, then icv(i−1) isopen;   Balance pressure between connected chamber and reset check valveto close;   and   Recalculate x(i), P_(R)(i) and P_(L)(i) until no moreopen check valve. Step 1 to N  Rotate wheel to a predefined step angle; Calculate new x(i), P_(R)(i) and P_(L)(i);  Determine check valvestatus:   If P_(R)(i) ≧ P_(L)(i)+Pcr then icv(i) is open;   IfP_(L)(i−1) ≧ P_(R)(i)+Pcr then cv(i−1) is open;   Balance pressurebetween connected chamber and reset check valve to close;   and  Recalculate x(i), P_(R)(i) and P_(L)(i) until no more open checkvalve.

The system 100 may also be exemplarily described:

Pump moved from θ to θ′ Force components ΔPA and mg cos (θ′) where ΔP =P_(L) − P_(R) check force balance for piston movement If ΔPA + mgcos(θ′) − mrα > 0 then piston moving to right ΔPA + mg cos(θ′) − mrα < 0then piston moving to left ΔPA + mg cos(θ′) − mrα = 0 then piston nomovement x: current piston position relative to piston center (−x_(o) ≦x ≦ x_(o)) calculate new position x′ by using ΔP′A + mg cos(θ′) − mrα =0 where ΔP′ = P_(L)′ − P_(R)′$P_{L}^{\prime} = {P_{L}\frac{{\left( {l + x} \right)A} + V_{d}}{{\left( {l + x^{\prime}} \right)A} + V_{d}}}$$P_{R}^{\prime} = {P_{R}\frac{{\left( {l - x} \right)A} + V_{d}}{{\left( {l - x^{\prime}} \right)A} + V_{d}}}$where l: chamber length at 0 position V_(d): dead-end volume(imcompressible) of each chamber α: Angular acceleration (typicallyaround 4 to 7 g) maintain -x_(o) ≦ x′ ≦ x_(o) If x′ > x_(o) then x′ =x_(o) If x′ < −x_(o) then x′ = −x_(o)

This system 100 (e.g., the air maintenance tire 10 described above) maybe a force control system with a maximum pumping capability determinedby the piston 16 moving a maximum distance to the right (FIG. 1), aslimited by one of the diaphragms 19, X(i)=Xo and APA >m(rα−g cos θ). Themaximum pumping pressure may be nΔP=n[m(rα−g cos θ)]/A psig. Forexample, a 50 g piston with a 5.0 mm diameter for 6 pumps at a constantspeed, (α=0), ΔP may be 21.74 psig. A 50 g piston with a 5.0 mm diameterfor 6 pumps at a 5.0 g acceleration, ΔP may be 130.43 psig. If theresistance, or cracking pressure Pcr, of the check valve 28 is notnegligible, the maximum pumping pressure ΔP may be n(ΔP−Pcr). Thus, thissystem 100 may be driven by two forces components, gravitation G andacceleration A. The gravitation force G may provide a high frequencycyclic effect on the pumps 18 in a short distance. The accelerationforce A may provide a low or medium frequency cyclic effect to ensuremaximum pumping pressure.

Under a first example condition, a piston mass effect under constantspeed, 6 pumps with 5.0 mm piston diameters, 4.0 mm length chambers(e.g., 101, 102), and 3.0 mm maximum travel may be mounted on a 15″wheel/tire (FIGS. 9A & 9B). Under a second example condition, a numberof piston effect under constant speed, 75.0 g pistons with 5.0 mmdiameters, 4.0 mm length chambers (e.g., 101, 102), and 3.0 mm maximumtravel may be mounted on a 15″ wheel/tire (FIGS. 10A & 10B).

While certain representative examples and details have been shown forthe purpose of illustrating the present invention, it will be apparentto those skilled in this art that various changes and modifications maybe made therein without departing from the spirit or scope of thepresent invention.

What is claimed:
 1. A system for use with a pneumatic tire mounted on awheel rim to keep the pneumatic tire from becoming underinflated, thesystem comprising: a plurality of pumps attached circumferentially tothe wheel rim, each pump having pump parameters; and a control valve forcontrolling inlet air into a tire cavity of the pneumatic tire, thecontrol valve having valve parameters, the system predicting systemperformance under various configurations and conditions through use ofthe pump parameters and the valve parameters.
 2. The system as set forthin claim 1 wherein the plurality of pumps and the control valve define amulti-chamber pump configuration.
 3. The system as set forth in claim 1wherein each pump includes one piston placed between two chambers. 4.The system as set forth in claim 3 wherein the two chambers areconnected by a narrow passage having a one-way check valve.
 5. Thesystem as set forth in claim 1 wherein: the pumps are fit to the wheelrim; set P_(R)(i)=P_(L)(i)=P₀, i=1 to n (total number of pumps used);set x(i)=0 and θ(i)=2π/n(i−1); P_(L)(0)=P₀ (always) andP_(R)(n+1)=P_(tire) (the tire cavity); calculate new x(i), P_(R)(i) andP_(L)(i); determine check valve status: if P_(R)(i)≧P_(L)(i)+Pcr, thencheck valve is open; if P_(L)(i−1)≧P_(R)(i)+Pcr, then adjacent checkvalve is open; balance pressure between connected chamber and resetcheck valve to close; and recalculate x(i), P_(R)(i) and P_(L)(i) untilno more open check valve.
 6. The system as set forth in claim 5 whereinsubsequently: the wheel rim rotates to a predefined step angle;calculate new x(i), P_(R)(i) and P_(L)(i); determine check valve status:if P_(R)(i)≧P_(L)(i)+Pcr then check valve is open; ifP_(L)(i−1)≧P_(R)(i)+Pcr then adjacent check valve is open; balancepressure between connected chamber and reset check valve to close; andrecalculate x(i), P_(R)(i) and P_(L)(i) until no more open check valve.7. The system as set forth in claim 1 wherein the plurality of pumpsdefine a force control system with a maximum pumping capabilitydetermined by a piston of each pump moving a maximum distance withineach pump.
 8. The system as set forth in claim 1 wherein each pumpincludes a first diaphragm limiting motion of a piston in a firstdirection and a second diaphragm limiting motion of the piston in asecond opposite direction.
 9. The system as set forth in claim 1 whereinthe system is driven by two force a gravitation component and anacceleration component.
 10. The system as set forth in claim 1 whereinthe pump parameters include a piston mass parameter, a first pistontravel parameter, and a second piston travel parameter.
 11. A system formodeling a pneumatic tire mounted on a wheel rim and a pumping mechanismmounted on the wheel rim to keep the pneumatic tire from becomingunderinflated, the system comprising: a plurality of pumps attachedcircumferentially to the wheel rim, each pump having pump parameters;and a control valve for controlling inlet air into a tire cavity of thepneumatic tire, the control valve having valve parameters, the systempredicting system performance under various configurations andconditions through use of the pump parameters and the valve parameters.12. The system as set forth in claim 11 wherein the plurality of pumpsand the control valve define a multi-chamber pump configuration.
 13. Thesystem as set forth in claim 11 wherein each pump includes one pistonplaced between two chambers.
 14. The system as set forth in claim 13wherein the two chambers are connected by a narrow passage having aone-way check valve.
 15. The system as set forth in claim 11 wherein:the pumps are fit to the wheel rim; set P_(R)(i)=P_(L)(i)=P₀, i=1 to n(total number of pumps used); set x(i)=0 and θ(i)=2π/n(i−1); P_(L)(0)=P₀(always) and P_(R)(n+1)=P_(tire) (the tire cavity); calculate new x(i),P_(R)(i) and P_(L)(i); determine check valve status: ifP_(R)(i)≧P_(L)(i)+Pcr, then check valve is open; ifP_(L)(i−1)≧P_(R)(i)+Pcr, then adjacent check valve is open; balancepressure between connected chamber and reset check valve to close; andrecalculate x(i), P_(R)(i) and P_(L)(i) until no more open check valve.16. The system as set forth in claim 15 wherein subsequently: the wheelrim rotates to a predefined step angle; calculate new x(i), P_(R)(i) andP_(L)(i); determine check valve status: if P_(R)(i)≧P_(L)(i)+Pcr thencheck valve is open; if P_(L)(i−1)≧P_(R)(i)+Pcr then adjacent checkvalve is open; balance pressure between connected chamber and resetcheck valve to close; and recalculate x(i), P_(R)(i) and P_(L)(i) untilno more open check valve.
 17. The system as set forth in claim 11wherein the plurality of pumps define a force control system with amaximum pumping capability determined by a piston of each pump moving amaximum distance within each pump.
 18. The system as set forth in claim11 wherein each pump includes a first diaphragm limiting motion of apiston in a first direction and a second diaphragm limiting motion ofthe piston in a second opposite direction.
 19. The system as set forthin claim 11 wherein the system is driven by two force a gravitationcomponent and an acceleration component.
 20. The system as set forth inclaim 1 wherein the pump parameters include a piston mass parameter, afirst piston travel parameter, and a second piston travel parameter.